Energy dependence of heavy-ion initial condition in isobar collisions

Abstract: Collisions of isobar nuclei, those with the same mass number but different structure parameters, provide a new way to probe the initial condition of the heavy ion collisions. Using transport model simulation of $^{96}$Ru+$^{96}$Ru and $^{96}$Zr+$^{96}$Zr collisions at two energies $\sqrt{s_{\mathrm{NN}}}=0.2$ TeV and 5.02 TeV, where $^{96}$Ru and $^{96}$Zr nuclei have significantly different deformations and radial profiles, we identify sources of eccentricities contributing independently to the final state harmonic flow $v_n$. The efficacy for flow generation differs among these sources, and explains the modest energy dependence of the isobar ratios of $v_n$. Additionally, a significant component of $v_n$ is found to be uncorrelated with the eccentricity but is instead generated dynamically during system evolution. Experimental measurement of these ratios at the LHC energy and comparison with RHIC energy can provide insight into the collision-energy dependence of the initial condition.